A known surface roughness tester brings its stylus into contact with the surface of a workpiece, moves the stylus along a surface of the workpiece, detects the displacement of the stylus caused by the surface roughness, and determines the surface roughness from the displacement (refer to Japanese Patent Application Publication No. 2000-74616, for example).
The lever-type detector mounted to the surface roughness tester illustrated in FIGS. 3 and 9 in Japanese Patent Application Publication No. 2000-74616 has a stylus that is brought into contact with the workpiece and a stylus holder that holds the stylus detachably.
Since styluses in various shapes are prepared beforehand for workpiece measurement portions having different shapes, in addition to the usual stylus, the operator of the surface roughness tester exchanges the stylus to one suitable for a workpiece measurement portion before starting measurement. For example, before starting measurement, the operator sets up a bore testing stylus to measure the surface roughness of a bore or sets up a deep-groove testing stylus having a long length to measure the surface roughness of a deep groove.
Besides the surface roughness tester, surface-property measuring machines such as a roundness measuring machine and a contour-shape measuring machine also have styluses in different shapes prepared for various workpiece measurement portions to deal with diversified kinds of measurement.
Conventionally, the operator exchanges the stylus. To do so, the operator temporarily stops the measurement, removes the current stylus from the detector, attaches a new stylus to the detector, and resumes the measurement.
In the conventional stylus exchanging procedure, the operator must stop the measurement temporarily and must detach the current stylus and attach a new one by hand. This interrupts the measurement for a long period of time and places a great deal of burden on the operator who exchanges the stylus. Accordingly, demand for automatic, unattended measurement by surface-property measuring machines has been growing in recent years.
The automatic probe changer used with three-dimensional measuring machines and the like could be applied to a surface-property measuring machine. The measuring machine may be equipped with an exchange rack storing different types of styluses, so that the stylus on the detector can be exchanged automatically.